This disclosure relates to turbomachinery, and more particularly, the disclosure relates to a shrouded turbine blade and method for making the same.
Gas turbine engines include a compressor that compresses air, a combustor that ignites the compressed air and a turbine across which the compressed air is expanded. The expansion of the combustion products drives the turbine to rotate, which in turn drives rotation of the compressor.
Gas turbine engines for applications such as helicopters incorporate a power turbine (PT) that is not mechanically coupled to the compressors in the gas generator portion of the gas turbine engine. The power turbine is rotationally driven by expanding gases from the gas generator portion to transmit power to a turboshaft. The turboshaft rotationally drives the helicopter propeller, typically at a constant speed, through a gearbox.
In order to increase efficiency, a clearance between the tips of the blades in the compressor, turbine and power turbine across the outer diameter of the flowpath is kept sufficiently small. This ensures that a minimum amount of air passes between the tips and the outer diameter. Turbine blades may incorporate a shroud to provide damping. Knife edges may be provided on the shroud to seal with respect to a blade outer air seal (BOAS) to maintain tight clearances.
The shroud adds mass to the end of the blade, which increases stress. One or more pockets may be provided on the shroud to reduce weight. For small diameter blades, traditional manufacturing approaches may prevent the pocket from being formed in the shroud.